1. Field of the Invention
The invention relates in general to a battery module and a charge/discharge method thereof, and more particularly to a battery module and a charge/discharge method thereof capable of sensing cell temperature by a positive temperature coefficient (PTC) device for appropriately adjusting the charge/discharge speed.
2. Description of the Related Art
With the rapid advance in electronic technology, various electronic devices are provided and used in people's business as well as leisure activities. Electronic devices have brought great convenience to the users. Electronic devices are powered by a battery module.
Referring to FIG. 1, a block diagram of a conventional battery module is shown. Conventional battery module 10 comprises a cell 110 and a charge/discharge circuit 140, wherein the cell 110 is a Li-Ion battery for example. The charge/discharge circuit 140 is coupled to the cell 110, and the cell 110 is charged by an external power received via the charge/discharge circuit 140. Also, the cell 110 provides power to an external electronic device via the charge/discharge circuit 140.
Referring to FIG. 2, a measured wave pattern of the voltage, the current and the temperature of a cell 110 is shown. The curve 210 denotes the temperature of the cell 110, the curve 220 denotes the voltage at the two ends of the cell 110, and the curve 230 denotes the current flowing through the cell 110.
The cell 110 is charged by the charge/discharge circuit 140 according to a constant current and constant voltage charge method. That is, the cell 110 is charged by a constant current first. Next, when the voltage at the two ends of the cell 110 reaches a constant voltage, the charge/discharge circuit 140 stops charging the cell 110. Afterwards, the current flowing through the cell 110 reduces to a minimum and gradually approaches 0.
However, such control method may easily result in an overheated and burnt cell. Besides, when the temperature is too high, the cell may even explode, further jeopardizing safety of use.